Canadian Dam Association Bulletin - Summer 2016 - 21
Figure 2: Flow Net of Dam with Impervious Blanket (USACE 1938)
TABLE 1: SUMMARY OF SEEPAGE ANALYSES
(at filter), i
Upstream impervious blanket
Sheet-pile cut-off wall (1/2 depth)
Just an impervious core
The upstream impervious blanket alternative was selected for the
dam. This alternative is presented on
3.5 Control of Internal Erosion
The potential for, and possible consequences of, internal erosion due to
seepage were recognized. In a report
Perecent Passing by Mass (%)
coarse-grained loose sands could
not be preserved so the specimens
were reconstituted and K measured.
The Kv of specimens of compact
sand and gravel was measured in
the sampling tubes. The fallinghead device was used for all soil
types except for coarse, uniform
sand and gravel. The constant-head
device was used on coarse, uniform
sand and gravel.
Based on the findings of the
study, the following assumptions
were made with respect to seepage
1. The foundation soils are anisotropic with a K h/Kv ratio of 4.
2. The core and the upstream blanket are impervious.
3. The value of K h for the dam (except
the core) and the foundation soils
above el. 85.3 m and below el. 79.2
m is 1.0x10-5 cm/s.
4. The value of Kv for the foundation
soils between el. 85.3 m and 79.2
m is 4.0x10-6 cm/s.
The hydraulic regimes of the
design alternatives were evaluated using flow nets (USACE 1938).
The results are summarized in
BASE LAYERS OF
Figure 3: Grain size distribution curves of the filters and foundation materials (from Brown 1940)
Canadian Dam Association * Summer 2016
Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Summer 2016